Inflatable boat with strengthened attachment of its rear board and method for fitting the latter

ABSTRACT

Inflatable boat (1) with two inflatable tubular chambers (2) secured along the two sides of a hull, a rear board (4) being secured in watertight fashion, laterally, to the two tubular chambers (2) and, at the bottom, to the rear edge of the hull, the means of securing the rear board (4) to each tubular chamber (2) comprising a sole (5) with U-shaped section made of a semi-rigid synthetic material secured by its bottom (6) to the tubular chamber (2) in such a way that the arms (7) of the U project radially from the tubular chamber and are secured to the lateral edge of the board (4) fitted between them, each lateral edge of the board (4) has two grooves (8) cut in it, one on each of its two faces, these grooves running parallel to this lateral edge and being filled with a synthetic material (9) secured to the walls at the groove. The two arms (7) of the sole (5) are secured respectively to the material (9) with which the grooves (8) are filled.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of allowed U.S. patent applicationSer. No. 09/017,544, filed Feb. 3, 1998, having the same title asappears above, now U.S. Pat. No. 5,960,734.

The present invention relates to improvements made to inflatable boatscomprising at least two inflatable tubular chambers bordering the twosides of a hull to which they are secured, a rear board closing the rearend of the boat and being secured in watertight fashion, laterally, tothe two inflatable tubular chambers and, at the bottom, to the rear edgeof the hull, in which boat the means of securing the rear board to eachinflatable tubular chamber comprise a sole with U-shaped sectionconsisting of a semi-rigid synthetic material and secured by its bottomto the inflatable tubular chamber in such a way that the arms of the Uproject out approximately radially from the inflatable tubular chamberand are secured to the lateral edge of the rear board fitted betweenthem.

More specifically, the invention relates to improvements made to thesecuring of the rear board to the lateral tubular chambers.

Known practice at the present time is for the rear board to be securedto each inflatable tubular chamber using a sole like the aforementionedone, by bonding and/or by bolting.

However, this method of assembly is not really satisfactory.

Because of the difference in materials of which the rear board(generally made of wood--for example marine-grade plywood) and the sole(generally made of synthetic material--for example polyvinylchloride)are made, the bonding is not as good as would be wished.

Furthermore, bolting, because of the loadings induced in the sole (theconnection needs to transmit the propulsive loading from the outboardmotor to the boat, via the rear board and the connecting sole) may, intime, cause tearing of the sole, making it necessary for this to bereplaced.

Finally, the phase of assembly work to be carried out in situ on theboat as it is being constructed in lengthy and relatively expensive.

The object of the invention is essentially to propose a structure and amethod of assembly which are improved, which lead to a mechanicallystronger connection and one which is easier and less expensive tomanufacture.

To these ends, an inflatable board like the one mentioned in thepreamble and designed in accordance with the invention, in essentiallycharacterized:

in that each lateral edge of the rear board has at least two grooves cutin it, one on each of its two main faces, these grooves runningapproximately parallel to this lateral edge of the said board and beingfilled with a synthetic material secured to the walls at the groove,

and in that the two arms of the sole are secured respectively to thematerial with which the said grooves of the rear board are filled.

Thanks to this design, it is possible to select materials which arecompatible for bonding or welding from which to make the sole and thematerial that fills the grooves in the rear board. Advantageously, thismay be the same material, for example polyvinylchloride, possiblyreinforced with fibres or fibrils, such as glass fibres. Securing usingthermal welding, with the contacting surfaces of synthetic materialsmelting together, leads to an assembly which is mechanically very strongand watertight.

Furthermore, the rear board can be prepared on a separate workstation,and the only remaining operation to be carried out when fitting it tothe boat is the welding, which can be done quickly.

In order to increase the mechanical strength transversely to the rearboard, provision may be made for each groove cut in the rear board tohave a trapezoidal dovetail-shaped section so that the filling materialbecomes more difficult to pull out of the groove.

Another solution that allows the connection to be reinforcedmechanically in a direction transversal to the rear board may consist inthe two grooves being arranged approximately opposite one another and inthe through-holes being made in the rear board between the two grooves,these holes being distributed, preferably uniformly, along the length ofthe grooves, the said holes too also being filled with syntheticmaterial.

Of course, it ig entirely possible for the aforementioned two provisionsto be combined in order to obtain maximum mechanical strength.

In practical terms, it is possible to provide a first strip ofsemi-rigid synthetic material, which has projecting pegs in registerwith the holes in the board, the said strip being forced into one grooveof the rear board with the pegs engaged in the aforementioned respectiveholes, and projecting into the other groove opposite and a second stripof semi-rigid synthetic material which has housings in register with theaforementioned holes in the board, the said second strip being forcedinto the other groove in the board with the said housings receiving theprojecting ends of the respective pegs; in this case, the aforementionedhousings are then advantageously through-holes and the projecting endsof the pegs come flush at least with the surface of the second strip.

More specifically, when producing a structure like the one describedimmediately above, the invention also proposes a method comprising thefollowing steps:

a sole of semi-rigid synthetic material with U-shaped section, the armsof which project approximately radially from the tubular chamber issecured to each said inflatable tubular chamber;

two grooves more or less opposite each other and running approximatelyparallel to each lateral edge of the board are made in the two mainfaces of the said rear board, the said grooves having a trapezoidaldovetail-shaped section;

through-holes are made through the rear board, these coming out into therespective bottoms of the two grooves opposite each other;

a first strip of semi-rigid synthetic material, with projecting pegswhich fit into the said holes in register, is inserted into one of thegrooves, the said first strip having a width at most equal to the widthof the opening of the groove and its surface extending beyond thecorresponding main face of the rear board, while the ends of the pegsprotrude beyond the opposite main face of the rear board;

a second strip of semi-rigid synthetic material, with through-holes inregister with the aforementioned holes and which fit over the pegs ofthe first strip, is inserted into the other groove, the said secondstrip having a width at most equal to the width of the opening of thegroove and its surface extending beyond the corresponding main face ofthe rear board;

the edge thus prepared of the rear board is fitted into thecorresponding sole;

and finally, the synthetic materials of which the sole and the stripsare made are heated in order to soften them and weld the pegs of thefirst strip to the second strip and weld the sole to the two stripswhile at the same time compressing the two strips opposite each other inorder to make the softened synthetic material flow to make it fill atleast most of the dovetail-shaped grooves,

by virtue of which the rear board and the sole are firmly assembled in away that can properly withstand both longitudinal loadings andtransverse loadings.

The invention will be better understood from reading the detaileddescription which follows of certain embodiments which are given merelyby way of non-limiting examples. In this description, reference is madeto the appended drawings in which:

FIG. 1 is a view in perspective, from behind, of an inflatable boatequipped with a rear board;

FIG. 2 is a view in section, on an enlarged scale, of an assembly inaccordance with the invention;

FIG. 3 is a view in section of one preferred embodiment of an assemblyin accordance with FIG. 1;

FIG. 4 is a view in section of another preferred embodiment of anassembly in accordance with FIG. 1;

FIGS. 5A, 5B, 5C illustrate, seen from the side, constituent elements ofa particularly preferred embodiment of an assembly in accordance withthe invention, for employing a method of manufacture in accordance withthe invention; and

FIGS. 6A, 6B, 6C illustrate diagrammatically, in section, three stagesin a method of manufacture in accordance with the invention using theelements of FIGS. 5A, 5B, 5C, FIG. 6C illustrating a particularlypreferred embodiment of an assembly in accordance with the invention.

Referring first of all to FIG. 1, this depicts diagrammatically, and inperspective, an inflatable boat 1 which comprises at least twoinflatable tubular chambers 2 bordering the two sides of a hull (notvisible, only the bottom 3 that covers it can be seen). In the exampledepicted, the two inflatable tubular chambers 2 are extended as far asthe front where they meet and together form an inflatable buoyancydevice in the overall shape of a U which is open at the back.

A rigid rear board 4 closes the rear end of the boat. The board 4 issecured in watertight fashion, laterally, to the two inflatable tubularchambers and, at the bottom, to the rear edge of the hull.

The means of securing the rear board 4 to each tubular chamber 2comprise a sole 5 with U-shaped section consisting of a syntheticmaterial and secured (for example welded or bonded) by its bottom 6 tothe inflatable tubular chamber 2 in such a way that the branches or arms7 of the U project out approximately radially from the inflatabletubular chamber 2 and are secured to the lateral edge of the rear board4 fitted between them.

Referring now to FIG. 2, in which the same references as in FIG. 1 havebeen kept to denote identical members, according to the arrangements inaccordance with the invention, each lateral edge of the rear board 4 hasat least two grooves 8 cut in it, one on each of its two main faces.These grooves 8 run approximately parallel to the lateral edge (which iscurved to mate with the external contour of the corresponding inflatabletubular chamber 2,--not shown in FIG. 2) of the said board 4.

The grooves 8 are filled with a synthetic material 9 (for examplepolyvinylchloride) which sticks firmly to the walls of the grooves.

In the assembled position shown in FIG. 2, the two arms 7 of the sole 5extend above and beyond the grooves 8 and are secured (for example bywelding or bonding) to the material 9 with which the grooves 8 arefilled.

Thanks to this arrangement, a bond which is robust and which is able towithstand and transmit the loadings exerted in all directions, bothloadings longitudinal to the boat (propulsive loadings imparted by anoutboard motor fixed to the rear board) and transverse loadings whichresult in shear loadings at the filler material 8/sole arms 7 joints, isproduced between the rear board and the inflatable tubular chamber.

Furthermore, it will be understood that the manufacturing process issimplified because each part involved in the assembly can be preparedand preassembled: the sole 5 is fixed in advance to the inflatabletubular chamber 2; the rear board 4 is machined in advance to have thegrooves 8, which are filled with material 9. If securing in obtained bybonding, the surfaces of the filler material 9 and/or the correspondingface of the arms 7 of the sole 5 are precoated with adhesive, thenassembly is performed by introducing the edge of the board 4 between theparted arms of the sole 5; if securing is obtained by welding, the boardis inserted into the sole, then electrodes are pressed onto the arms tocause the respective synthetic materials to soften and fuse together.

The simplification and speeding-up of the assembly lead to anappreciable reduction in the cost of manufacturing this part of theboat.

The provisions set out hereinabove can be contrived in various ways witha view to increasing the mechanical strength of the assembly and also tomaking the assembly process even simpler.

As depicted in FIG. 3, it is possible to give the grooves 8 atrapezoidal or dovetail-shaped section, with an opening at the surfacewhich is narrower than the bottom of the groove, so that the length offiller material 9 trapped in the groove 8 is held in mechanically (notcounting the adherence of the material to the walls of the groove 8).

As depicted in FIGS. 2 to 4, it is possible to contrive for the twogrooves 8 which are on the two main faces, along one lateral edge of therear board 4 to be arranged approximately opposite each other. It isthen possible, as shown in FIG. 4, to provide through-holes 10 made inthe rear board between the two grooves 8 opposite each other, theseholes 10 being distributed, preferably uniformly, along the length ofthe grooves. The grooves 10 too are also filled with synthetic material,so that in this way bridges 9a of synthetic material are made betweenthe lengths 9 of material filling the grooves 8.

In an especially preferred embodiment illustrated in FIG. 6C, thespecial arrangements of FIGS. 3 and 4 are combined so that the fillermaterial 9 is secured to the rear board 4 in a way which has maximumstrength. The mechanical strength of the block of synthetic fillermaterial is considerably increased as it is then, so to speak, embeddedin the rear board 4 and forms part of it.

A particularly simple, quick and economical implementation of the saidespecially preferred embodiment may be as follows.

The rear board 4 is prepared (FIG. 5A) with, along each lateral edge,two grooves 8 more or less opposite each other and with adovetail-shaped section, and a succession of open holes 10, more or lessuniformly distributed along the length of the grooves 8.

A first strip 11 (FIG. 5B) of semi-rigid synthetic material ismanufactured (the strip is therefore deformable, and in particular canbe curved as shown in FIG. 5B so that it conforms to the longitudinalcurvature of the grooves 8). The strip 11 is given a set of pegs 12which project from one of its faces and are integral (monobloc) with it.It will be noted that the width d of the face of the strip bearing thepegs 12 is at most equal to the width d₁ of the opening of the grooves8, furthermore the spacing of the pegs 12 on the strip 11 is identicalto the spacing of the holes 10 in the grooves 8.

A second strip 13 (FIG. 5C) of semi-rigid synthetic material (preferablythe same material as was used for the first strip 11) is alsomanufactured. The strip 13 has housings 14, such as through-holes, whichhave the same spacing as the through-holes 10 in the grooves 8 and sizedto accommodate the pegs 12 of the first strip 11. The second strip 13too, has a width which is smaller than the width of the opening of thegrooves 8 and is preferably the same width d as the first strip.

The two strips 11 and 13 may, for example, be made of PVC filled withglass fibres, preferably long fibres.

For fitting, the first strip 11, curved beforehand, is introduced intoone of the grooves 8, the pegs 12 passing through the holes 10 andemerging in the other groove 8 opposite, then the second strip 13, alsoalready curved, is inserted into the other groove 8 in such a way thatits housings 14 fit over the ends of the pegs 12 (FIG. 6A).

It will be noted here that as illustrated in FIG. 6B, the strips 11 and13 have thicknesses which slightly exceed the depth of the respectivegrooves 8, so that the upper faces of the strips project slightly beyondthe corresponding main faces of the rear board 4. Furthermore, thehousings 14 here are through-holes, and the length of the pegs 12 issuch that their free end protrudes beyond the upper face of the secondstrip, and therefore beyond the corresponding main face of the rearboard 4.

The lateral edge of the board thus prepared is then inserted into thesole S, the arms 7 thereof tightly gripping the strips 11, 13. Thenelectrodes (depicted diagrammatically by arrows 15 in FIG. 6C) areapplied to the arms 7 and heat up the synthetic materials situatedbetween them at the same time as they are clamped together to compressthese materials. The heated and softened synthetic materials aretherefore forced to melt superficially at the same time as, becausethere is excess material on account of the increased thickness of thestrips, softened material is forced to flow towards the edges of thedovetail-shaped grooves and to fill these grooves.

It will thus be understood that the method in accordance with theinvention makes the assembly process simpler, so this process becomesquicker and therefore more economical.

As goes without saying and as is already evident from the above, theinvention is not in any way restricted to those of its applications andembodiments which have been more specifically envisaged; on thecontrary, it encompasses all alternative forms thereof.

We claim:
 1. An inflatable boat comprising:a. at least one inflatablechamber; b. a rear board defining at least one groove thereon; c. a soleformed of semi-rigid synthetic material and secured to the chamber; andd. a synthetic material placed in the groove to secure the sole to therear board by thermal welding of the sole and synthetic material.
 2. Aninflatable boat according to claim 1 in which the rear board is made atleast partially of wood.